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Related Concept Videos

Electrocardiogram01:29

Electrocardiogram

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An electrocardiogram (ECG or EKG) is a critical diagnostic tool that records the electrical signals produced by the heart during each heartbeat. This recording is achieved through electrodes placed strategically on the arms, legs, and chest. The electrocardiograph amplifies these signals and produces 12 distinct tracings, offering a comprehensive understanding of the heart's electrical activity.
Three major waveforms are present in a typical ECG recording: the P wave, the QRS complex, and...
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Electrocardiogram Fundamentals01:28

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Introduction
An electrocardiogram (ECG) is a diagnostic tool for identifying cardiac conditions such as arrhythmias, conduction abnormalities, and myocardial ischemia.
Definition
An electrocardiogram (ECG) visualizes the heart's electrical activity by tracing the electrical movement associated with each heartbeat on a graph or monitor. As the heart beats, an electrical wave passes through it, correlating with the cardiac cycle events.
Parts of an ECG
An ECG utilizes electrodes on the skin...
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Correlation between ECG and Cardiac Cycle01:25

Correlation between ECG and Cardiac Cycle

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The electrical signals recorded on an electrocardiogram (ECG) occur before the mechanical processes of contraction and relaxation during the cardiac cycle.
A cardiac action potential originates in the SA node and spreads throughout the atria and the AV node in approximately 0.03 seconds. This results in the P wave in an ECG and triggers atrial contraction. The action potential is then briefly slowed at the AV node, allowing the atria to contract and fill the ventricles with blood before...
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ECG Interpretation of Rhythms01:24

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An electrocardiogram (ECG)graphically represents the heart's electrical activity on ECG paper or a monitor.
Components of the Electrocardiogram
The primary components of a normal ECG waveform in Normal sinus rhythm(NSR) include the P wave, PR interval, QRS complex, ST segment, T wave, and occasionally a U wave.
ECG waveforms are divided by vertical and horizontal lines at standard intervals.
The horizontal axis measures time and rate, and the vertical axis measures amplitude or voltage....
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ECG Interpretation of Arrhythmias II: Atrial, Junctional and Ventricular Arrhythmias01:25

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Arrhythmia is a condition characterized by an irregular heart rhythm, with ECG changes that differ based on its origin and nature. The types of arrhythmias discussed below include atrial, junctional, and ventricular arrhythmias.Atrial ArrhythmiasPremature Atrial Complexes (PACs): PACs are early atrial beats caused by stress, caffeine, alcohol, electrolyte imbalances, hypoxia, hyperthyroidism, or certain medications (e.g., bronchodilators and decongestants). The ECG shows early P waves with an...
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Dysrhythmias V: Evaluating Dysrhythmias01:30

Dysrhythmias V: Evaluating Dysrhythmias

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Dysrhythmias, also known as arrhythmias, are disturbances in the heart's rhythm that range from benign to life-threatening. A thorough evaluation is crucial for appropriate management and involves a comprehensive medical history, physical examination, and various diagnostic tests.Medical HistorySymptoms: Collect detailed information on palpitations, dizziness, syncope, chest pain, and fatigue. Note their onset, frequency, and triggers.Previous Cardiac Issues: Document any history of heart...
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Predicting inappropriate S-ICD® episodes by simple 12-lead surface ECG parameters.

Jan Wagner1, Benjamin Rath1, Kevin Willy1

  • 1Department of Cardiology II - Electrophysiology, University Hospital Muenster, Muenster, Germany.

Journal of Electrocardiology
|June 6, 2021
PubMed
Summary

A preimplantation electrocardiogram (ECG) can predict inappropriate S-ICD® shocks. QRS-T wave discordance in lead I is a significant predictor, especially in hypertrophic cardiomyopathy patients.

Keywords:
12-lead electrocardiogramInappropriate therapySubcutaneous defibrillatorT-wave oversensing

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Area of Science:

  • Cardiology
  • Biomedical Engineering

Background:

  • Subcutaneous Implantable Cardioverter-Defibrillators (S-ICD®) offer protection against sudden cardiac death.
  • Inappropriate shocks from S-ICD® systems are a concern, often caused by oversensing.
  • Predictive markers for these inappropriate episodes are crucial for patient management.

Purpose of the Study:

  • To evaluate the predictive role of a preimplantation 12-lead electrocardiogram (ECG) for inappropriate S-ICD® episodes.
  • To identify specific ECG parameters associated with oversensing and subsequent inappropriate shocks.

Main Methods:

  • A cohort of 116 patients with S-ICD® and at least 6 months follow-up was analyzed.
  • Preimplantation 12-lead ECGs were assessed for QRS and T-wave amplitude, concordance/discordance, and QRS/T wave ratio using Datinf® Measure software.
  • Results were correlated with occurrences of inappropriate S-ICD® episodes due to oversensing.

Main Results:

  • Of 116 patients, 17 (14.7%) experienced 27 inappropriate shocks, primarily due to T-wave oversensing.
  • Hypertrophic cardiomyopathy (HCM) was a significant risk factor (OR 6.16, p=0.004).
  • QRS-T wave discordance in lead I independently predicted inappropriate shocks (OR 6.5, p=0.003); the combination of HCM and lead I discordance increased risk 8.4-fold (p=0.003).

Conclusions:

  • Preimplantation ECG analysis, specifically QRS-T wave discordance in lead I, is a valuable tool for predicting inappropriate S-ICD® shocks.
  • This finding holds particular importance for patients with hypertrophic cardiomyopathy.
  • Identifying these ECG patterns can help mitigate the risk of inappropriate therapy in S-ICD® recipients.